Forgejo <=16.0.3 Critical RCE

Posted by weierstass 18 hours ago

Forgejo <=16.0.3 Critical RCE(codeberg.org)

186 points | 68 comments

amiga386 16 hours ago|

You should change the URL to https://codeberg.org/forgejo/forgejo/milestone/139655

> PR: Critical: fix: prevent template expansion from interfering with git repo initialization. When generating a new repository from a template repository, Forgejo clones the template repository, removes the .git folder, performs variable template expansion on files listed in .forgejo/template, and initializes a new git repository. During this process, variable template expansion could be misused in order to create a new .git folder, which git would adopt and incorporate during its initialization of a new git repository. A malicious template repository could be used to read arbitrary data from the Forgejo host, and to execute arbitrary processes on the Forgejo host, as a remote code execution attack. To address this issue, after variable expansion is completed, any existing .git folder is removed from the directory before the git repository is initialized.

embedding-shape 14 hours ago||

Conciser: User's who can create new repositories, can exploit templates to do variable template expansion leading to being able to read arbitrary data from the Forgejo hosts.

If you have open registrations or otherwise users you don't 100% trust with the ability to create new repository (which is the default I think?), they could potentially exploit this and you probably wanna upgrade ASAP.

If you have only trusted users, or single user, seems it's fine. Of course, wanna upgrade anyway to not add escalation paths, but in the other situation it's graver.

amluto 10 hours ago||

> To address this issue, after variable expansion is completed, any existing .git folder is removed from the directory before the git repository is initialized.

What happened to sandboxing the offending git invocation?

techknowlogick 16 hours ago||

Only posting here because I've been asked about it. Gitea is protected against both of these issues.

(bias note: part of project leadership of Gitea)

Edit: As a note, security incidents happen to everyone and we shouldn't shame anyone for reporting them, especially as that'd otherwise cause less issues to be reported overall.

tredre3 15 hours ago||

> Gitea is protected against both of these issues.

Is Gitea's immunity just incidental because it was written by a different person, or is it due to a deliberate defensive system that prevents such bug/mistake from occurring?

embedding-shape 14 hours ago||

Very interested in knowing too, since the issues seems to not be related at all, or similar, so now this must mean a Gitea "project leader" would only say this if they have some sort of layer that doesn't require them to manually patch issues individually. Meaning, firewall? Would be weird if that's built-in into Gitea though... Hmm.

Macha 11 hours ago|||

It looks like Gitea made the same fix (rm -r .git after template processing) back in February: https://github.com/go-gitea/gitea/commit/2176e84ab977011ff2b...

PR: https://github.com/go-gitea/gitea/pull/36734

So likely Gitea < 1.25.5 was vulnerable.

ntauthority 3 hours ago|||

i like how this is a side effect of a bunch of assorted changes in a commit and PR solely described as "Fix path resolving" making it hard for anyone running Gitea to even know this is a security fix

wvbdmp 3 hours ago||

It’s explicitly listed as a security fix in the release notes, accompanied by a CVE: https://blog.gitea.com/release-of-1.25.5/

fartfeatures 8 hours ago|||

It is unfortunate nobody tipped anyone off downstream.

vanschelven 1 hour ago||

given the fact that they communicated about this as a CVE, and Forgejo is a fork of gitea, one could say that this is on Forgejo though.

jonstaab 13 hours ago|||

Forgejo is a fork of gitea.

ThePowerOfFuet 12 hours ago||

Hence the question...

dabeeeenster 12 hours ago|||

Your note is really important! Thanks for adding it. None of us are perfect.

keel-control 16 hours ago||

This was my first thought after they disallowed LLM contributions.

They may not use AI to check for vulnerabilities but attackers are going to which puts themselves at the disadvantage.

burkaman 15 hours ago||

They did not disallow LLM contributions, and they definitely didn't disallow using LLMs to research security vulnerabilities. They only disallowed projects that are majority LLM-written.

https://codeberg.org/Codeberg/org/commit/71149c7fc95ccfeae36...

badsectoracula 15 hours ago||

That is about Codeberg, not Forgejo.

Forgejo disallows LLM contributions, including using a "general AI" (they include LLMs under "general AI") for reviews[0]:

> 5. Using general AI for review is forbidden. If the change contains changes to the UX it has to be approved by a human reviewer.

[0] https://codeberg.org/forgejo/governance/src/branch/main/AIAg...

burkaman 14 hours ago|||

Ah sorry, didn't realize they had their own policy. This is a little stronger, but you can certainly still use an LLM to search for vulnerabilities, you would just need to write fixes yourself and mention if you used an LLM for assistance.

The rule you quoted is about code reviews, they don't want you using an LLM to write reviews or leave comments.

This is a pretty poorly written policy to be honest, so I understand if you interpret it to mean "no LLMs in any capacity", but I think if that's what they meant they would have said that. In fact they explicitly allow content "made with the help of AI", you just have to disclose it.

imtringued 2 hours ago||

Their definition of vibe coding is pretty whacky.

>Vibe coding is the practice where AI creates a code change (feature, bug fix, tests, refactor) with a human that describes what needs to be implemented.

So if you let an AI prompt another AI without human input, that's not vibe coding? Meanwhile if you prompt the model with pseudo code you've written or code written in another programming language to translate into the target language, that's vibe coding?

>It is not allowed to use AI in an autonomous-looking way to contribute in Forgejo.

They used the word "in", meaning it could refer to organizational membership, their repo or theoretically any instance of Forgejo, including self hosted ones. They failed to specify what part of Forgejo or the definition of Forgejo they meant.

Overall this is a pretty poorly written document and when you think about it, it doesn't really matter how poorly written it is when they are basically 100% against AI.

overfeed 14 hours ago||||

> Forgejo disallows LLM contributions

You're misreading the rule.

>> 5. Using general AI for review is forbidden.

The second sentence makes it even clearer, as it would have been unnecessary under a blanket ban scenario

>> ... If the change contains changes to the UX it has to be approved by a human reviewer.

semiquaver 10 hours ago||

This looks unambiguous to me:

  > Forgejo does not accept works of authorship (code, documentation, etc.) either partially or completely generated by AI due to legal uncertainties.

thayne 10 hours ago||

Using AI to find a vulnerability is not a work of authorship. Using the AI generated text as your bug report would be, but if you use AI to find a bug, then write up a report yourself, I think that would be fine.

dessimus 8 hours ago|||

>If the change contains changes to the UX it has to be approved by a human reviewer.

Would that not imply that a change that does not effect the UX does not have to be approved by a human reviewer? Otherwise, why specifically call out "changes to the UX" and not say "all changes"?

otherme123 16 hours ago|||

Was this discovered by AI? Is all AI code 100% free of bugs?

You are implying that just by allowing LLM contributions your product is free of bugs, and the LLM won't introduce new bugs. Of course, if the LLM introduces bugs, the solution is to add another layer of LLM looking for bugs, ad infinitum.

Another post from today from Shopify, praising LLM to code their frontend, also stated that their LLM generated code is not ready to deploy, and needs to be reviewed:

> It’s tempting to just point an LLM to the React Native codebase and try to one-shot the same features in native, but it doesn’t work. Even if you ask it to gather as much information as it can up front, freeze that into specs, task files, and then implement it, you end up with a huge amount of unmaintainable code that can’t be shipped. [...] each [build] must prove its behavior with tests, match the running app in a visual review, survive two adversarial code reviewers, and get a human's nod before it's committed and the next one starts.

cmrdporcupine 11 hours ago|||

> You are implying that just by allowing LLM contributions your product is free of bugs

That... is not the implication of the comment you're replying to.

You don't need to make it all fundamentalist.

1matin 16 hours ago|||

> They may not use AI to *check for vulnerabilities*

you didn't read the comment, did you?

titularcomment 16 hours ago|||

I really disagree with their acceptable usage policy, but you can't say it with certainity that LLM contributions would be a fix for this. They generate so much noise (as the primary incentive behind an independent LLM scan is often cheap contributor brownie points for your CV) that it also could lead to bogus PRs being approved or helpful PRs being lost in the noise.

bdcravens 15 hours ago|||

Why can't you use an LLM to find vulnerabilities and then hand-code the fix? You don't even have to clean-room implement it; let the LLM write the code, and then reimplement, doing what you can to de-LLM-ify it.

omnimus 15 hours ago|||

You can. People on Codeberg use LLMs. They are just against spam of low quality projects generated with LLMs.

cmrdporcupine 11 hours ago||

That is actually entirely not what they were saying at the time of the vote and its aftermath. At all.

Go back and read the threads. On this forum, or on mastodon, or on the vote. It was pretty vociferously ... shall we say ... "principled"

It was never stated to be about "low quality" but about use in "large part" or "majority", and when pressed people refused to define what that meant, and in fact got angry and defensive and said things like "you'll know if you've crossed the line" and "stop trying to force consent" and similar pearls of wisdom.

The post-facto rationalization did in fact leave them room to judge "quality" on a purely subjective basis. I didn't stick around to find out how that would shake out.

mitxela 6 hours ago||

Do you expect it to be enforced by a machine? Why would you need a precise definition of "majority"?

pixl97 13 hours ago|||

You can, though some people are going to be annoyed by it and just publish a zero day out of spite.

striking 16 hours ago||

Disallowing LLM contributions doesn't disqualify the use of LLMs to identify vulnerabilities.

iCarrot 3 hours ago||

Using LLMs for automated security audit looks like it could fall under the definition of "vibe coding" or "agent mode", which is strictly forbidden

>6. It is not allowed to use AI in an autonomous-looking way to contribute in Forgejo. This also applies when someone engages in 'vibe coding' or uses so-called 'agent mode'.

Macha 16 hours ago||

Since the release notes is currently unreadable due to codeberg rate limits, the two fixes in the release notes are:

https://codeberg.org/forgejo/forgejo/pulls/14301:

*Critical:* fix: prevent template expansion from interfering with git repo initialization. When generating a new repository from a template repository, Forgejo clones the template repository, removes the `.git` folder, performs variable template expansion on files listed in `.forgejo/template`, and initializes a new git repository. During this process, variable template expansion could be misused in order to create a new `.git` folder, which git would adopt and incorporate during its initialization of a new git repository. A malicious template repository could be used to read arbitrary data from the Forgejo host, and to execute arbitrary processes on the Forgejo host, as a remote code execution attack. To address this issue, after variable expansion is completed, any existing `.git` folder is removed from the directory before the git repository is initialized.

https://codeberg.org/forgejo/forgejo/pulls/14301:

ensure authorization reducer is accessed when checking editable PRs in APIs. When editing a git repo contents through Forgejo's API, a specialized security control is used to permit repository maintainers to edit branches that they do not own when an open pull request with the "allow maintainer edit" option is present. This specialized security control did not take into account API-specific security restrictions, such as repo-specific access tokens. As a result, it was possible for an API access token with restricted permission to make modifications outside of that restricted permission. The specialized security control has been updated to take into account API authentication security restrictions.

---

So if like me you run a private forgejo instance with closed signups and limited repository creation, you can wait for the update. Otherwise maybe take it off the public internet for a bit?

nirui 1 hour ago||

I'm just reading the code here:

  // Before template expansion, .git was removed so that a fresh repo can be initialized; remove it again in case
  // some template variable usage has conflicted with this directory and impacts git operations.
  if err := root.RemoveAll(".git"); err != nil {
    return fmt.Errorf("unable to remove .git folder")
  }

Why the `err` isn't carried by the error message? For security? Then maybe log it internally?

User/operator can't really fix the problem if you keep giving them information this vague.

jzebedee 16 hours ago||

Relevant change:

   Security bug fixes

    PR: Critical: fix: prevent template expansion from interfering with git repo initialization. When generating a new repository from a template repository, Forgejo clones the template repository, removes the .git folder, performs variable template expansion on files listed in .forgejo/template, and initializes a new git repository. During this process, variable template expansion could be misused in order to create a new .git folder, which git would adopt and incorporate during its initialization of a new git repository. A malicious template repository could be used to read arbitrary data from the Forgejo host, and to execute arbitrary processes on the Forgejo host, as a remote code execution attack. To address this issue, after variable expansion is completed, any existing .git folder is removed from the directory before the git repository is initialized.

hephaes7us 16 hours ago|

It looks like this is a bit less concerning if you have turned off open account registration.

rcleveng 16 hours ago||

``` This git endpoint is seeing a high influx of requests for this repository, to preserve the availability of Codeberg your search request will not be processed. Sorry for the inconvenience and please try again later. ```

Any mirror?

sbx320 16 hours ago||

The PR is still accessible https://codeberg.org/forgejo/forgejo/pulls/14300

    Critical: fix: prevent template expansion from interfering with git repo initialization. When generating a new repository from a template repository, Forgejo clones the template repository, removes the .git folder, performs variable template expansion on files listed in .forgejo/template, and initializes a new git repository. During this process, variable template expansion could be misused in order to create a new .git folder, which git would adopt and incorporate during its initialization of a new git repository. A malicious template repository could be used to read arbitrary data from the Forgejo host, and to execute arbitrary processes on the Forgejo host, as a remote code execution attack. To address this issue, after variable expansion is completed, any existing .git folder is removed from the directory before the git repository is initialized.

n3mes1s 17 minutes ago||

I'm working on a tool to reproduce stuff like this exactly.

Yep this is an RCE with the forgejo user on the host.

https://www.pruva.dev/reproductions/REPRO-2026-00345 for details.

you can even start your version of the repro using github codespaces

========================================

REPRO-2026-00345

========================================

Title: Forgejo <16.0.4 RCE via crafted template repository (.forgejo/template expansion recreates .git folder adopted by git init)

Severity: CRITICAL

CVE: CVE-2026-89094

========================================

[pruva] Working directory: /workspaces/pruva-sandbox/pruva-results/REPRO-2026-00345

[pruva] Found script artifact: bundle/repro/reproduction_steps.sh

[pruva] Downloaded 4 repro artifact(s), script: 324 lines

[pruva] ==========================================

[pruva] WARNING: This will execute code that

[pruva] exploits a real vulnerability.

[pruva] ==========================================

[pruva] Auto-confirming in sandbox environment...

[pruva] Running reproduction script...

--- REPRODUCTION OUTPUT ---

[09:39:29] ensuring container images are present

[09:39:42] vulnerable image digest: sha256:214f4ae63ee78be1e445e58573c88dc7215e72091210852e0df94eaac1a25685

[09:39:42] fixed image digest: sha256:a263a1298e89e0bdf019005ce1927e9aadaa8f1bd2a94a3e66ad94e2a89e19ce

[09:39:42] [vuln-1] starting container (codeberg.org/forgejo/forgejo:16.0.3-rootless)

[09:39:52] [vuln-1] service healthy on 127.0.0.1:4011

[09:39:53] [vuln-1] admin user + token ready

[09:39:55] [vuln-1] malicious template pushed

[09:40:03] [vuln-1] generate API returned 201

[09:40:15] [vuln-1] marker=**** hook_id=**** hostdata=**** readme_ok=**** gen=201

[09:40:15] [vuln-2] starting container (codeberg.org/forgejo/forgejo:16.0.3-rootless)

[09:40:25] [vuln-2] service healthy on 127.0.0.1:4012

[09:40:26] [vuln-2] admin user + token ready

[09:40:28] [vuln-2] malicious template pushed

[09:40:32] [vuln-2] generate API returned 201

[09:40:36] [vuln-2] marker=**** hook_id=**** hostdata=**** readme_ok=**** gen=201

[09:40:36] [fixed-1] starting container (codeberg.org/forgejo/forgejo:16.0.4-rootless)

[09:40:40] [fixed-1] service healthy on 127.0.0.1:4111

[09:40:40] [fixed-1] admin user + token ready

[09:40:41] [fixed-1] malicious template pushed

[09:40:46] [fixed-1] generate API returned 201

[09:40:50] [fixed-1] marker=false hook_id=false hostdata=false readme_ok=**** gen=201

[09:40:50] [fixed-2] starting container (codeberg.org/forgejo/forgejo:16.0.4-rootless)

[09:40:52] [fixed-2] service healthy on 127.0.0.1:4112

[09:40:53] [fixed-2] admin user + token ready

[09:40:54] [fixed-2] malicious template pushed

[09:40:58] [fixed-2] generate API returned 201

[09:41:02] [fixed-2] marker=false hook_id=false hostdata=false readme_ok=**** gen=201

[09:41:02] vuln markers: **** / **** ; hook-id: **** / **** ; hostdata: **** / **** ; gen: 201 / 201

[09:41:02] fixed markers: false / false ; readme-ok: **** / **** ; gen: 201 / 201 runtime_manifest.json written with 44 proof artifacts

[09:41:02] VERDICT: CONFIRMED - remote code execution reproduced on Forgejo 16.0.3 via crafted template repository; fixed 16.0.4 unaffected

--- END REPRODUCTION OUTPUT ---

[pruva] ==========================================

[pruva] VERIFICATION SUCCESSFUL

[pruva] Duration: 93s

[pruva] ==========================================

[pruva] Logs: /workspaces/pruva-sandbox/pruva-results/REPRO- 2026-00345/logs/ - fixed-1 - fixed-2 - reproduction_steps.log - vuln-1 - vuln-2

[pruva] Results saved to: /workspaces/pruva-sandbox/pruva-results/REPRO-2026-00345

[pruva] Keeping work directory: /workspaces/pruva-sandbox/pruva-results/REPRO-2026-00345 Outcome: success User: vscode WorkspaceFolder: /workspaces/pruva-sandbox

tugback 1 hour ago||

Removing .git after expansion seems fragile. Sandboxing the git step would close the whole class of bugs.

mmsc 13 hours ago|

Wonder how long it took from report to patch. IME codeberg has one of the rudest security teams in oss (fair enough or not, irrelevant). https://news.ycombinator.com/item?id=47941590 Is quite relevant

embedding-shape 13 hours ago||

Is that linked submission "your experience" or is there something else you're basing that on? Because that article you linked is kind of strange, read through the comments on what you linked.

mfenniak 13 hours ago||

Forgejo's security team received disclosure of this issue on September 4th. (source: I am a member of that team)

johnsea 1 hour ago||

(Thanks for your work!)

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